Aliphatic acid sulfonate modified polyamides

ABSTRACT

USUAL POLYAMIDE-FORMING STARTING SUBSTANCES ARE CONDENSED IN THE PRESENCE OF ALIPHATIC SULFONATES OR SULFONATE ESTERS TO OBTAIN POLYAMIDES HAVING A PARTICULARLY GOOD DYE AFFINITY.

Patented Apr. 4, 1972 US. Cl. 26078 R 4 Claims ABSTRACT OF THE DISCLOSURE Usual polyamide-forming starting substances are condensed in the presence of aliphatic sulfonates or sulfonate esters to obtain polyamides having a particularly good dye affinity.

The present invention relates to modified polyamides and a process for making them.

In the interests of economy it is important to simplify the dyeing processes for textiles of all kinds. In this respect, man-made fibers offer interesting possibilities. For example, the affinity for a determined class of dyestuff can be varied to a large extent by an appropriate chemical modification of the spinning material. Textiles made of correspondingly differing fibers or filaments can therefore be dyed different colors in a single dyebath by using dyestuffs each of which has a determined affinity for a determined type of fiber. This is valuable and desirable with a view to the possibilities of arranging the colors and in order to simplify storage, particularly in the case of piece-goods. Moreover, a frequent readjust ment of the machines is dispensed with.

Technical processes have been known particularly in the field of polyamides. When polyamide fibers having different capacities of binding acid are, for example, dyed with acid dyestuffs, tints of gradated intensity are obtained. Contrary multicolor effects cannot, however, be obtained by combining such fibers. For this purpose, special types are required which, contrary to normal polyamide, remain substantially reserved when dyeing with, for example, acid dyestuffs, but can be dyed with basic dyes. By combining such types of polyamide fibers with normal polyamide fibers, contrary colors can be obtained in a single bath. As this is a selective dyeing with different dyestuffs, each color can be varied in intensity independently of the other. The dyeing conditions, particularly the pH value of the bath, are also of importance in this case.

The affinity of polyamides for acid dyestuffs depends on the salt formation with the terminal amino groups. To obtain polyamides having a reduced affinity for acid dyes, the number of the terminal amino groups has therefore been reduced, for example, by a reaction with carboxylic acids or carboxylic acid esters which have been added to the melt. To improve the affinity of polyamides for basic dyestuffs which is in itself only small, strongly acid groups of, for example, sulfuric acid nature, must be introduced.

Modified polyamides, the afiinity of which for acid dyestuffs is more or less reduced, but which can be dyed with basic dyes, can be obtained by incorporating aromatic and araliphatic sulfocarboxylic acids or the sulfonates thereof, for example those of the alkali metals. In these known modifiers the sulfo group is attached to the aromatic nucleus or to an alkoxy side chain.

In general, compounds with two carboxylic acid or carboxylic acid ester groups are used; they are chosen to obtain an improved incorporation in the polymer chains. In effect, however, the chain terminating effect is very pronounced due to the excess of carboxyl groups so that the degree of polycondensation necessary to obtain useful fibers is not obtained in many cases. On the other hand, the metal sulfonates of the sulfomonocarboxylic acids of the group of the above known aromatic and araliphatic sulfocarboxylic acids are in many cases only insufficiently soluble in the reaction mixture. Consequently, the amounts thereof that can be used are too small to obtain a satisfactory effect or too long times of polycondensation are required or difficulties in spinning may arise.

Now we have found that valuable modified polyamides which have only a small affinity for acid dyestuffs, but a good affinity for basic dyestuffs can be obtained by carrying out the polycondensation of the usual polyamide forming starting materials in the presence of derivatives of organic sulfonic acids, advantageously of sulfonates and/or sulfonate esters of at least one branched or unbranched aliphatic sulfocarboxylic acid containing 2 to 18 carbon atoms, 1 or 2 sulfonic acid groups and 1 or 2 carboxyl groups, used in an amount within the range of from 0.05 to 10 mol percent, calculated on the monomer unit of the unmodified polyamide. The carboxyl groups of the sulfonate esters are esterified with a low aliphatic alcohol with 1 to 6 carbon atoms, for example, methanol, ethanol, nand i-propanol, n-butanol, n-pentanol and n-hexanol. In the sulfonate groups, particularly the ions of lithium, sodium and potassium form the cations. Mixtures of the sulfonates with sulfonate esters may likewise be used.

The above number of 2 to 18 carbon atoms of the aliphatic sulfocarboxylic acids is not intended as a limitation, but is the preferable number, i.e. derivatives of aliphatic sulfocarboxylic acids with more than 18 carbon atoms may also be used. It could not be foreseen that sulfonates and sulfonate esters of aliphatic sulfocarboxylic acids also make suitable modifiers for the manufacture of polyamides as the thermostability of these compounds is inferior to that of the derivatives of aromatic and araliphatic sulfonic acids known as polyamide modifiers and since these compounds are exposed to considerable thermal stress during polycondensation. It was particularly surprising that the sulfonates and esters of a-sulfocarboxylic acids, in which two functional groups are linked to the same carbon atom are sufficiently stable to withstand the thermal stress during polycondensation. Especially these compounds have proved useful for the manufacture of the desired modified polyamides. They can obviously particularly well be incorporated in the macromolecule because of their simple structure.

Examples of suitable polyamide modifiers are the following substances (for clarity, only the basic compounds and not their sulfonates or sulfonate esters have been enumerated): sulfoacetic acid, 2-sulfopropionic acid, 3-sulfopropionic acid, 4 sulfobutyric acid, 2-sulfoisobutyric acid, 2-sulfo-4-hydroxybutyric acid, 2-sulfopalmitic acid, 2-sulfostearic acid, u-sulfophenylacetic acid, Z-sulfoadipic acid, 2,5-disulfoadipic acid and 2-sulfovinyl-acetic acid. Compounds of this type may also contain inert substituents, for example, alkyland alkoxy groups or halogen atoms. Particularly good dyeing effects are obtained with the use of derivatives of aliphatic sulfocarboxylic acids containing hydroxyl groups. The derivatives of the said compounds may be used as such as in admixture with one another.

The sulfonates and sulfonate esters of aliphatic sulfocarboxylic acids are easy to obtain. Halogenated carboxylic acid esters may, for example, be reacted with metal sulfites, or carboxylic acids may be sulfonated and the sulfocarboxylic acids primarily formed may be converted into the sulfonates or the esters thereof. The sulfonate esters are in many cases more easy to obtain synthetically than the free carboxylic acids and are therefore advantageously used for the process of the invention.

As polyamide-forming starting substances for the manufacture of the modified polyamides in accordance with the invention any known polyamide-forming substance may be used, preferably the lactams, aminocarboxylic acids and neutral salts of dicarboxylic acids and diamines commonly used for this purpose, for example, -e-CE1PI'O- lactam, e-aminocaproic acid and the neutral salt of hexamethylene-diamine and adipic acid (hexamethylenediammonium adipate, designated hereinafter AH-salt).

The modifiers are generally added in the form of the solid, finely powdered substances or in the form of an aqueous solution thereof. The addition is advantageously made at the beginning of the polycondensation which is carried out in the same manner as without modifiers. It is also possible to add them at another moment during or after the polycondensation. Small amounts of other substances, for example, dulling agents or substances protecting against the action of light, may also be added.

In the polycondensation of lactams, for example, 6- caprolactam, it is advantageous, in order to obtain high final viscosities of the melts, to carry out the reaction in the presence of Water with or without the application of pressure, while adding 2 to 10% by weight of AH-salt or e-aminocaproic acid. By proceeding in this manner, a polymeric material of excellent tinctorial properties which has a relative viscosity Within the range of from 2.7 to 3.1 determined in a solution of 0.2 gram of polymer in 20 mil liliters of H 80 of 95.5% strength is obtained. For carrying out the polycondensation in practice, the apparatus commonly used for the manufacture of polyamide may be used. Vessels provided with stirring means and a descending distillation tube are particularly advantageous.

The products obtained by the process of the invention are colorless. Their melting points differ only little from those of unmodified polyamides. They can easily be formed by the usual methods, for example spun on extruders to drawable filaments. The extraction with hot water usually carried out to remove proportions of low molecular weight may be carried out before or after forming.

The shaped articles made from the polyamides of the invention, for example, films, fibers and filaments, have substantially no receptivity for acid dyestuffs, but are dyed deep tints by basic dyestuffs. By dyeing mixtures of these fibers with normal polyamide fibers in a single bath, using acid and basic dyes together, contrary multicolor effects of high brilliance can therefore be obtained. The following examples serve to illustrate the invention, but are not intended to limit it.

EXAMPLE 1 In a vessel with stirring means, 40 kilograms of caprolactam were melted under a nitrogen atmosphere. At a temperature of 160 C., 2.4 kilograms of AH salt, 60 grams of titanium dioxide in the form of a aqueous dispersion, 300 grams of the sodium sulfonate of sulfoacetic acid and 3.2 grams of manganese acetate-4H O were added. The temperature was raised to 260 C. within 2 hours, water and a small amount caprolactam being distilled off. The melt was kept at 260 C. until the melt viscosity remained almost unchanged, which could be recognized by the performance of the stirring means. The melt was then discharged into cold water and the solidified white polyamide was made into chips. The granular product was extracted three times at 95 C. with three times the amount of distilled water and dried under strongly reduced pressure. The relative viscosity, determined in a solution of 0.2 gram polyamide in milliliters sulfuric acid of 95.5 strength, was 2.89. The chips were spun in known manner from the melt and the resulting tow was drawn at a ratio of 123.6. The filament so obtained was dyed only little by acid dyes, but was dyed deep tints by basic dyes. When the polyamide fibers were used in admixture with unmodified polyamide fibers, excellent contrary multicolor effects were obtained in a single dyebath with combinations of acid and basic dyestuffs. Because of its high relative viscosity, the filament is very suitable for the manufacture of tufted carpets.

By using, instead of the sodium sulfonate of sulfoacetic acid, 330 grams sulfoacetic acid potassium sulfonate, the same good result was obtained.

EXAMPLE 2 The polycondensation was carried out in the manner described in Example 1, but while using, instead of the sodium sulfonate of sulfoacetic acid, 280 grams of the sodium sulfonate of sulfoacetic acid methyl ester. A polyamide of a relative viscosity of 2.92 determined in the manner described in Example 1 was obtained which could very well be spun and drawn. The filament had exactly the same good tinctorial properties as the filament of Example 1.

EXAMPLE 3 A mixture of 550 grams of caprolactam, 33 grams of AH salt and 4.5 grams of the sodium sulfonate of 2- sulfopropionic acid was melted under nitrogen and heated to 270 C. within 2 hours, while stirring. The process was then carried out in a manner analogous to that of Example 1. The colorless polyamide so obtained had a relative viscosity of 3.03 determined in the manner described in Example 1 and had the tinctorial properties described in Example 1.

EXAMPLE 4 In the manner described in Example 3, 550 grams of caprolactam, 33 grams of AH salt and 4.4 grams of the sodium sulfonate of 4-sulfobutyric acid were polycondensed. The resulting polyamide had a relative viscosity of 3.05 determined as described in Example 1, and could very well be dyed different colors in the manner described in Example 1.

EXAMPLE 5 4.7 grams of the sodium sulfonate of 2-sulfoisobutyric acid were polycondensed in the manner described in Example 3 with the amounts of caprolactam and AH salt also indicated in that example. The resulting polyamide had a relative viscosity of 3.10 determined as described in Example 1 and the same good tinctorial properties as the polyamide of Example 1.

EXAMPLE 6 The process was carried out in the manner described in Example 3, but while using, instead of the sodium sulfonate of 2-sulfopropionic acid, 8.8 grams of the sodium sulfonate of 2-sulfopalmitic acid. The polyamide so obtained had a relative viscosity of 3.00 determined in the manner described in Example 1, and could be excellently dyed in the manner described in Example 1.

EXAMPLE 7 In a vessel provided with stirring means, 550 grams of caprolactam and 33 grams of AH salt were polycondensed at 270 C. under nitrogen until the melt had a relative viscosity of 3.1 determined in the manner described in Example 1. 5.6 grams of the sodium sulfonate of a-SlllfO- phenylacetic acid methyl ester were then added and the mixture was stirred for a further 30 minutes at 270 C. The melt was then discharged into cold water and the product was obtained in the manner described in Example 1. A modified polyamide was obtained which had a viscosity of 2.75 determined as described in Example 1, and which after being spun in admixture with normal poly= amide fibers could be used for producing multicolor ef-- fects in the manner described in Example 1.

EXAMPLE 8 550 grams of caprolactam, 33 grams of AH salt and grams of the sodium sulfonate of 2-sulfo-4-hydroxybutyric acid were polycondensed in a manner analogous to that of Example 3. The polyamide so obtained had a relative viscosity of 2.77 determined as described in Example 1, and could particularly well be dyed in the manner also described in that example.

EXAMPLE 9 550 grams of caprolactam and 33 grams of AH salt were polycondensed in the manner described in Example 3 while adding 6.1 grams of the sodium sulfonate of 2- sulfoadipic acid. The resulting polyamide had a relative viscosity of 2.80 determined as described in Example 1, and could be dyed different colors in the manner described in Example 1.

What is claimed is:

1. A modified fiber forming aliphatic polycarbonamide produced by polycondensation of aliphatic polycarbonamide-forming substance for said polyamide in the presence of 0.05 to 10 mol percent, calculated on the monomer unit of the unmodified polyamide, of at least one alkali metal snlfonate and/or sulfonate ester of a branched or unbranched aliphatic sulfocarboxylic acid containing 2 to 18 carbon atoms, 1 or 2 sulfonic acid groups and 1 or 2 carboxyl groups.

2. Modified polycaprolactam produced by polycondensation of aliphatic polycarbonamide-forming substance for said polyamide in the presence of 0.05 to 10 mol percent, calculated on the monomer unit of the unmodified polyamide, of at least one alkali metal sulfonate and/or sulfonate ester of a branched or unbranched aliphatic sulfocarboxylic acid containing 2 to 18 carbon atoms, 1 or 2 sulfonic acid groups and 1 or 2 carboxyl groups.

produced by polycondensation of aliphatic polycarbonamide-forming substance for said polyamide in the presence of 0.05 to 10 mol percent, calculated on the monomer unit of the unmodified polyamide, of at least one alikali metal sulfonate and/or sulfonate ester of a branched or unbranched aliphatic sulfocarboxylic acid containing 2 to 18 carbon atoms, 1 or 2 sulfonic acid groups and l or 2 carboxyl groups.

References Cited UNITED STATES PATENTS 2,473,924 6/ 1949 Walker 260-78 3,235,533 2/1966 Brinkman 260-78 3,296,204 1/1967 Caldwell 260-78 HAROLD D. ANDERSON, Primary Examiner US. Cl. X.R.

8-55; 260-48 A, 78 L, 78 SC 

